I know nothing about games, but took quick look at the gog site. The game itself says it can be run on Linux, but the "gog downloader" only lists ability to work on Windows and Mac from what I saw. (I did not spend a lot of time looking through support section, so maybe there is a version of the download software for Linux and I just didn't see it.) Can you just do a regular download of the game instead of trying to download it with the special gog downloader?